Our research aims at elucidating the molecular mechanisms involved in the regulation of gene expression in animal cells. In particular, we are studying the mode of action of steroid hormones on cloned neoplastic cell lines in tissue culture. The system under investigation is the mechanism of killing of murine lymphoid cell lines by glucocorticoids. We will pursue the isolation of variants of lymphoid cells resistant to glucocorticoids and the characterization, by genetic and biochemical means, of the defects responsible for resistance.